Removing null or undefined from Angular observable

Issue

I am doing Angular state management using BehaviourSubject, but while pushing the data to store is adding undefined value to the end of the object (creating another undefined value). can any one suggest the way to remove?

{todos:[{"accountNo":"91957869","vpainfo":[{"vpa":"saasasa@fff"}]},undefined]}

The below are the sample snippets,

behaviourStore.ts

import {Observable, BehaviorSubject} from 'rxjs';

export class Store<T> {
    state$: Observable<T>;
    private _state$: BehaviorSubject<T>;

    protected constructor (initialState: T) {
        this._state$ = new BehaviorSubject(initialState);
        this.state$ = this._state$.asObservable();
    }

    get state (): T {
        return this._state$.getValue();
    }

    setState (nextState: T): void {
        this._state$.next(nextState);
    }
}

behaviourState.ts

export interface User {
    accountNo?: string;
    vpainfo: VPAinfo[]
  }
  export interface VPAinfo {
    vpa?: string;
  }
  export class BehaviourState {
    todos: User[]
  }

behaviourReducer.ts

import { Injectable } from '@angular/core';
import { Store } from './behaviourStore';
import { BehaviourState } from './behaviourState';
import * as fromActions from '../actions/users.actions';

@Injectable()
export class BehaviourReducer extends Store<BehaviourState> {
    constructor() {
        super(new BehaviourState());
    }
    callReducer(action: any) {
        switch (action.type) {
            case fromActions.ADD_TODO:
                this.setState({ ...this.state, todos: [action.payload.todo, ...this.state.todos] });
                break;
        }
    }
}

And finally adding the data in the below way,

const resultobj = {"accountNo":"91957869","vpainfo":[{"vpa":"saasasa@fff"]};
const action = { type: fromActions.ADD_TODO, payload: { todo: resultobj}};
this.behaviourReducer.callReducer(action);

Solution

Since you have not defined any default value for todos. It's showing undefined.

Try this:

export class BehaviourState {
    todos: User[] = [];
 }

Answered By - Chellappan வ